add a flag to enable use of upper 4mb memory in DS mode

src/NDS.cpp

@@ -444,7 +444,7 @@ void NDS::Reset()
     else
     {
         ARM9ClockShift = 1;
-        MainRAMMask = 0x3FFFFF;
+        MainRAMMask = useExtendedMemory ? 0x7FFFFF : 0x3FFFFF;
     }
     // has to be called before InitTimings
     // otherwise some PU settings are completely
@@ -4345,4 +4345,9 @@ void NDS::ARM7IOWrite32(u32 addr, u32 val)
     Log(LogLevel::Debug, "unknown ARM7 IO write32 %08X %08X %08X\n", addr, val, ARM7.R[15]);
 }
 
+void NDS::SetMemoryExtension(bool enabled)
+{
+    useExtendedMemory = enabled;
+}
+
 }

src/NDS.h

@@ -469,6 +469,8 @@ public: // TODO: Encapsulate the rest of these members
     virtual void ARM7IOWrite16(u32 addr, u16 val);
     virtual void ARM7IOWrite32(u32 addr, u32 val);
 
+    void SetMemoryExtension(bool enabled);
+
 #ifdef JIT_ENABLED
     [[nodiscard]] bool IsJITEnabled() const noexcept { return EnableJIT; }
     void SetJITArgs(std::optional<JITArgs> args) noexcept;
@@ -527,6 +529,7 @@ private:
     void EnterSleepMode();
     template <CPUExecuteMode cpuMode>
     u32 RunFrame();
+    bool useExtendedMemory = false;
 
 public:
     NDS(NDSArgs&& args, void* userdata = nullptr) noexcept : NDS(std::move(args), 0, userdata) {}

src/frontend/qt_sdl/EmuInstance.cpp

@@ -1353,6 +1353,7 @@ bool EmuInstance::updateConsole(UpdateConsoleNDSArgs&& _ndsargs, UpdateConsoleGB
             nds = new NDS(std::move(ndsargs), this);
 
         NDS::Current = nds;
+        nds->SetMemoryExtension(localCfg.GetBool("Debug.ExtendedMemory"));
         nds->Reset();
         loadRTCData();
         //emuThread->updateVideoRenderer(); // not actually needed?

src/frontend/qt_sdl/EmuSettingsDialog.cpp

@@ -109,6 +109,8 @@ EmuSettingsDialog::EmuSettingsDialog(QWidget* parent) : QDialog(parent), ui(new
     ui->cbGdbBOSA9->setDisabled(true);
 #endif
 
+    ui->cbDebugExtendedMem->setChecked(instcfg.GetBool("Debug.ExtendedMemory"));
+
     on_chkEnableJIT_toggled();
     on_cbGdbEnabled_toggled();
     on_chkExternalBIOS_toggled();
@@ -301,6 +303,7 @@ void EmuSettingsDialog::done(int r)
             instcfg.SetBool("Gdb.ARM7.BreakOnStartup", ui->cbGdbBOSA7->isChecked());
             instcfg.SetBool("Gdb.ARM9.BreakOnStartup", ui->cbGdbBOSA9->isChecked());
 #endif
+            instcfg.SetBool("Debug.ExtendedMemory", ui->cbDebugExtendedMem->isChecked());
 
             cfg.SetInt("Emu.ConsoleType", ui->cbxConsoleType->currentIndex());
             cfg.SetBool("Emu.DirectBoot", ui->chkDirectBoot->isChecked());

src/frontend/qt_sdl/EmuSettingsDialog.ui

@@ -580,7 +580,7 @@
          </property>
         </widget>
        </item>
-       <item row="5" column="0">
+       <item row="6" column="0">
         <spacer name="verticalSpacer_4">
          <property name="orientation">
           <enum>Qt::Vertical</enum>
@@ -614,7 +614,14 @@
          </property>
         </widget>
        </item>
-       <item row="5" column="0" colspan="7">
+       <item row="5" column="0" colspan="5">
+        <widget class="QCheckBox" name="cbDebugExtendedMem">
+         <property name="text">
+          <string>Enable extended main RAM (8Mb)</string>
+         </property>
+        </widget>
+       </item>
+       <item row="7" column="0" colspan="7">
         <widget class="QLabel" name="label_18">
          <property name="text">
           <string>Note: melonDS must be restarted in order for these changes to have effect</string>